Composite ball bat with constrained layer dampening

ABSTRACT

A composite ball bat includes one or more dampening elements located primarily at or near one or more vibration anti-nodes of the ball bat to provide vibration dampening and improved bat “feel.” The dampening elements may be made of viscoelastic and/or elastomeric materials, and/or other vibration-attenuating materials, and may be located in the barrel, the handle, and/or the tapered or transition region of the ball bat.

This application is a Continuation-In-Part of U.S. patent application Ser. No. 11/078,782, filed Mar. 11, 2005, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/903,493, filed Jul. 29, 2004. This application is also a Continuation-In-Part of U.S. patent application Ser. No. 11/034,993, filed Jan. 12, 2005, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/903,493, filed Jul. 29, 2004. Each of the above-listed patent applications is incorporated herein by reference.

BACKGROUND

When a baseball bat or softball bat impacts a ball, energy is transferred from the ball to the bat, in the form of deformation (radial and transverse), noise, and heat. When the ball strikes a location of the bat that is in the proximity of a primary vibration node, and/or at the intersection of a primary vibration node and the center of percussion (COP) of the bat, the bat experiences little or no vibration. This is known as a “sweet spot” hit. Alternatively, when the ball strikes a location of the bat that is not in the vicinity of a primary vibration node or the COP, the bat deforms into its fundamental and harmonic mode shapes. The magnitude of this deformation is a direct function of the mode that is excited and the distance from the vibration node and the COP to the impact location. If the acceleration of the bat into its mode shapes is significantly high, and is at a specific frequency, the bat will vibrate and produce shock waves.

Shock waves travel at a high velocity and, depending upon their energy, can actually sting a player's hands. Sting typically results from displacements in the bat handle caused by rigid body rotations resulting from impact away from the COP, and/or from modal vibrations caused by impact away from the primary vibration nodes of the ball bat. Impacts of this nature are commonly referred to as “off-center hits,” because the “sweet spot” of a bat barrel is typically located at approximately the center of its length where the COP and the first primary vibration node are in close proximity to one another. The sting resulting from off-center hits may be distracting and painful to the player, and is therefore undesirable. To minimize sting, and improve the “feel” of the bat, shock waves resulting from off-center hits must be absorbed or otherwise attenuated prior to reaching the bat's handle.

SUMMARY

In a composite ball bat, one or more dampening elements are located primarily at or near one or more vibration anti-nodes of the ball bat to provide vibration dampening and improved bat “feel.” The dampening elements may be made of viscoelastic and/or elastomeric materials, and/or other vibration-attenuating materials, and may be located in the barrel, the handle, and/or the tapered or transition region of the ball bat.

Other features and advantages of the invention will appear hereinafter. The features of the invention described above can be used separately or together, or in various combinations of one or more of them. The invention resides as well in sub-combinations of the features described.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein the same reference number indicates the same element throughout the several views:

FIG. 1 is a side view of a ball bat.

FIG. 2 is a partial sectional view of Section X of FIG. 1.

FIG. 3A is a magnified view of Section Y of FIG. 2, according to one embodiment.

FIG. 3B is a magnified view of Section Y of FIG. 2, according to another embodiment.

FIG. 3C is a magnified view of Section Y of FIG. 2, according to another embodiment.

FIG. 4 is a side view of a ball bat showing the conceptual locations of the predominant vibration anti-nodes of the ball bat, according to one embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will now be described. The following description provides specific details for a thorough understanding and enabling description of these embodiments. One skilled in the art will understand, however, that the invention may be practiced without many of these details. Additionally, some well-known structures or functions may not be shown or described in detail so as to avoid unnecessarily obscuring the relevant description of the various embodiments.

The terminology used in the description presented below is intended to be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific embodiments of the invention. Certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this detailed description section.

Turning now in detail to the drawings, as shown in FIG. 1, a baseball or softball bat 10, hereinafter collectively referred to as a “ball bat” or “bat,” includes a handle 12, a barrel 14, and a tapered section or transition region 16 joining the handle 12 to the barrel 14. The free end of the handle 12 includes a knob 18 or similar structure. The barrel 14 is preferably closed off by a suitable cap, plug, or other end closure 20. The interior of the bat 10 is preferably hollow, which facilitates the bat 10 being relatively lightweight so that ball players may generate substantial bat speed when swinging the bat 10.

The ball bat 10 preferably has an overall length of 20 to 40 inches, more preferably 26 to 34 inches (a 34 inch bat is shown in FIG. 4 by way of example only). The overall barrel diameter is preferably 2.0 to 3.0 inches, more preferably 2.25 to 2.75 inches. Typical bats have diameters of 2.25, 2.625, or 2.75 inches. Bats having various combinations of these overall lengths and barrel diameters, as well as any other suitable dimensions, are contemplated herein. The specific preferred combination of bat dimensions is generally dictated by the user of the bat 10, and may vary greatly between users.

The bat barrel 14 may be a single-wall or a multi-wall structure. If it is a multi-wall structure, the barrel walls may optionally be separated by one or more interface shear control zones (ISCZs), as described in detail in incorporated U.S. patent application Ser. No. 10/903,493. Any ISCZ used preferably has a radial thickness of approximately 0.001 to 0.010 inches, more preferably 0.005 to 0.006 inches. Any other suitable size ISCZ may alternatively be used.

An ISCZ may include a bond-inhibiting layer, a friction joint, a sliding joint, an elastomeric joint, an interface between two dissimilar materials (e.g., aluminum and a composite material), or any other suitable element or means for separating the barrel into “multiple walls.” If a bond-inhibiting layer is used, it is preferably made of a fluoropolymer material, such as Teflon® (polyfluoroethylene), FEP (fluorinated ethylene propylene), ETFE (ethylene tetrafluoroethylene), PCTFE (polychlorotrifluoroethylene), or PVF (polyvinyl fluoride), and/or another suitable material, such as PMP (polymethylpentene), nylon (polyamide), or cellophane.

In one embodiment, one or more ISCZs may be integral with, or embedded within, layers of barrel material, such that the barrel 14 essentially acts as a one-piece/multi-wall construction. In such a case, the barrel layers at at least one end of the barrel are preferably blended together to form the one-piece/multi-wall construction. The entire ball bat 10 may also be formed as “one piece.” A one-piece bat design, as used herein, generally refers to the barrel 14, the tapered section 16, and the handle 12 of the ball bat 10 having no gaps, inserts, jackets, or bonded structures acting to appreciably thicken the barrel wall(s). In such a design, the distinct laminate layers are preferably integral to the barrel structure so that they all act in unison under loading conditions. To accomplish this one-piece design, the layers of the bat 10 are preferably co-cured, and are therefore not made up of a series of connected tubes (inserts or jackets) each having a separate wall thickness at the ends of the tubes.

The blending of the barrel walls into a one-piece construction, around one or more ISCZs, like tying the ends of a leaf spring together, offers a stable, durable assembly, especially for when impact occurs at the extreme ends of the barrel 14. Bringing multiple laminate layers together assures that the system acts as a unitized structure, with no one layer working independent of the others. By redistributing stresses to the extreme ends of the barrel, local stresses are reduced, resulting in increased bat durability. In an alternative multi-wall embodiment, the bat and/or barrel layers are not blended together at either end.

The one or more barrel walls are preferably each made up of one or more composite plies. The composite materials that make up the plies are preferably fiber-reinforced, and may include fibers of glass, graphite, boron, carbon, aramid (e.g., Kevlar®), ceramic, metallic, and/or any other suitable structural fibrous materials, preferably in epoxy form or another suitable form. Each composite ply preferably has a thickness of approximately 0.002 to 0.060 inches, more preferably 0.005 to 0.008 inches. Any other suitable ply thickness may alternatively be used.

In one embodiment, the bat barrel 14 may comprise a hybrid metallic-composite structure. For example, the barrel may include one or more walls made of composite material(s), and one or more walls made of metallic material(s). Alternatively, composite and metallic materials may be interspersed within a given barrel wall. In another embodiment, nano-tubes, such as high-strength carbon nano-tube composite structures, may alternatively or additionally be used in the barrel construction.

FIG. 2 illustrates an interior section of one embodiment of a bat barrel 14 including one or more vibration dampening elements, or dampeners 30, incorporated into the composite layers 32 of the bat barrel 14. The one or more dampeners 30 may be made of any suitable vibration attenuating or dampening material(s), i.e., any material(s) having a lower axial elastic modulus than that of the neighboring or surrounding materials in the ball bat. In one embodiment, one or more of the dampeners 30 may have an axial elastic modulus that is 0.01 to 50%, or 0.02 to 25%, or 0.05 to 10%, or 0.10 to 5.0%, or 0.50 to 2.5%, or 0.75 to 1.25%, of the axial elastic modulus of the neighboring or surrounding materials in the ball bat 10. Any material having a lower elastic modulus than the neighboring or surrounding materials in the ball bat 10 may be used, however.

In one embodiment, one or more of the dampeners 30 are made of one or more viscoelastic and/or elastomeric materials, such as elastomeric rubber, silicone, gel foam, or other similar materials. The dampeners 30 may alternatively or additionally be made of any other suitable dampening materials, including but not limited to PBO (polybenzoxazole), UHMWPE (ultra high molecular weight polyethylene, e.g., Dyneema®), fiberglass, dacron® (“polyethylene terephthalate”—PET or PETE), nylon® (polyamide), certran®, Pentex®, Zylon®, Vectran®, and/or aramid, that are effective at dissipating or otherwise attenuating vibrational energy relative to the neighboring or surrounding materials in the ball bat 10.

Thus, depending on the one or more materials that are used to form the structural layers of the ball bat 10, a wide variety of dampening materials (relative to those neighboring or surrounding structural materials) may be used in the ball bat 10. For example, a soft rubber dampening material may have an axial elastic modulus of approximately 10,000 psi, whereas a “dampening” material such as aramid may have an axial elastic modulus of approximately 12,000,000 psi. While the dampening effect of aramid is significantly less than that of a typical soft rubber material, it may still have an appreciable dampening effect on surrounding or neighboring structural bat material(s) having an even higher axial elastic modulus, and it may provide increased durability relative to softer materials. Accordingly, materials having a relatively high axial elastic modulus, such as aramid, may be used as effective dampeners in some ball bat constructions.

Each dampener 30 may form part of one or more of the composite layers within the ball bat 10, or may be included as a separate layer. Each dampener 30 may also optionally be sandwiched between neighboring composite layers, as shown in FIG. 3A. Each dampener 30 is preferably bonded, fastened, or otherwise attached or fused to the surrounding composite material in the ball bat 10. The composite material at one or both ends of the ball bat 10, and/or at locations adjacent to one or both ends of the dampener 30, may also be fused or blended together to provide a continuous load path between the bat structure and the dampener 30.

In the embodiment illustrated in FIG. 3A, the dampener 30 is shown located substantially at the mid-plane of a barrel wall, where shear stresses are the highest, by way of example only. One or more dampeners 30 may alternatively or additionally be located anywhere within the radial thickness of the one or more barrel walls that make up the bat barrel 14, or within any of the other regions of the ball bat 10. FIG. 3B, for example, illustrates an embodiment in which a dampener 30 is located at an inner portion of a barrel wall. In this embodiment, at least one inner layer of composite material preferably confines the dampener 30 within the barrel structure, and preferably extends at least one inch or more beyond each end of the dampener 30. In another embodiment, one or more dampeners 30 may additionally or alternatively be similarly positioned at an outer portion of one or more barrel walls, or other bat regions.

FIG. 3C shows an embodiment in which multiple dampeners 30 are positioned in series within a single layer at the inner portion of a barrel wall. In another embodiment, multiple dampeners 30 may additionally or alternatively be located in parallel, i.e., positioned at approximately the same longitudinal location of the ball bat 10 at different radial locations within the barrel 14 or other bat region. If the ball bat 10 includes a multi-wall barrel 14, and/or one or more ISCZs, dampeners 30 may be located in one or more of the barrel walls, at any suitable locations, including at the plane between adjacent barrel walls and/or against one or both sides of an ISCZ. Thus, one or more dampeners 30 may be located anywhere within the barrel 14, the transition region 16, and/or the handle 12 of the ball bat 10 to achieve a desired response, as further described below.

The one or more dampeners 30 may each have any suitable length and/or thickness. For example, a dampener 30 may be 0.25 to 5.00 inches in length (or longer, if desired), and 0.004 to 0.100 inches thick (or any other suitable thickness). In one embodiment, each dampener has a thickness of 0.008 to 0.020 inches. While the dampeners 30 may be any conceivable size, and could theoretically run approximately the entire length of the ball bat 10, it is preferable to incorporate one or more discrete dampeners of smaller size, at one or more strategic locations, to selectively dampen vibration while not adding substantial weight to, or significantly lowering the durability of, the ball bat 10.

FIG. 4 illustrates one embodiment of a 34 inch ball bat 10, including the locations of the predominant vibration anti-nodes of the ball bat 10. An anti-node is a point in a standing wave at which the amplitude is a maximum. Thus, under impact conditions, the vibration anti-nodes of the ball bat 10 are located at the regions of maximum deflection (specific to the mode shape of the bat in vibration) in the ball bat 10. The vibration anti-nodes, as used herein, generally refer to anti-nodes of the bending and/or hoop modes of the ball bat 10. The locations of one or more of these vibration anti-nodes, which are readily determinable by those skilled in the art, may vary depending on the overall dimensions and makeup of the ball bat 10. Thus, the specific anti-node locations illustrated in FIG. 4 are shown by way of example only.

In one embodiment, one or more vibration dampeners 30 are located at, and are optionally substantially centered about, one or more of the vibration anti-nodes in the ball bat 10 to reduce the amplitude of vibrations excited at those locations by off-center hits. Alternatively, one or more dampeners 30 may be located adjacent to or substantially near one or more of the vibration anti-nodes, since deflection is also relatively high at bat regions near the anti-nodes. Terms and phrases used herein to describe dampener location, such as “substantially at” or “at or near,” generally refer to the idea that a dampener is ideally located directly at an anti-node location, but that a dampener could alternatively or additionally be located near an anti-node to produce a dampening effect. Thus, such language is intended to mean that a dampener may be located directly at an anti-node, or very close to the anti-node.

The one or more dampeners 30 reduce the amplitude of impact reaction forces and modal vibrations by absorbing significant shear strain energy and dissipating it into the environment in the form of heat energy. A dampener 30 made from a viscoelastic material, for example, dissipates energy at a lower rate (due to hysteresis) than a typical elastic material, such that dissipation of the impact energy occurs relatively slowly, resulting in high dampening of the initial impact impulse.

One preferred location for a dampener 30 is at or near the anti-node of the first bending mode (i.e., of the fundamental harmonic) of the ball bat 10, indicated by a “1” in FIG. 4. The anti-node of the first bending mode exhibits the largest deformation, and the highest strain energy, of all the anti-nodes of the principal modes. Thus, by locating one or more dampeners 30 at or near the anti-node of the first bending mode, i.e., at approximately 19 to 21 inches from the cap end of the ball bat 10 shown in FIG. 4, a large amount of vibration energy resulting from off-center hits may be dissipated or otherwise attenuated.

One or more dampeners 30 may also be located at or near the anti-nodes of the second and/or third bending modes (which do not exhibit as much deformation as does the anti-node of the first bending mode, but which still contribute to vibrational effects) of the ball bat 10, indicated by the numbers “2” and “3”, respectively, in FIG. 4, to suppress the second and/or third bending modes. To suppress the second bending mode of the ball bat 10 illustrated in FIG. 4, for example, one or more dampeners 30 may be positioned at approximately 8 to 10 inches, and/or 26 to 28 inches, from the cap end of the ball bat 10.

In another embodiment, a dampener 30 is additionally or alternatively positioned at or near the anti-node of the fundamental or first hoop mode, indicated by the letter “A” in FIG. 4, of the ball bat 10. Because this anti-node, which is located approximately 4 to 8 inches from the cap end of the ball bat 10 illustrated in FIG. 4, is substantially at the intersection of the COP and the first and second harmonic bending nodes (i.e., at the “sweet spot” of the ball bat), minimal, if any, vibration occurs at this location. Thus, only a minimal amount of vibration attenuation (if any) is required at this location to prevent sting. By adding one or more dampeners 30 at or near this “sweet spot” location, however, the perceived size of the sweet spot generally increases, providing improved feel for batters.

Multiple dampeners 30 may be located throughout the bat structure, at or near any combination of the anti-nodes, to minimize vibrations in the ball bat 10. Each of the dampeners 30 is preferably discrete and discontinuous with respect to other dampeners 30, and is located primarily at or near a single anti-node. It is contemplated, however, that one or more individual dampeners 30 could overlap two or more anti-nodes. For example, a single dampener 30 could be positioned to overlap the anti-node “1” of the first bending mode and the anti-node “3” of the third bending mode located in the transition region of the ball bat (e.g., at approximately 19-22 inches from the cap end of the ball bat 10 illustrated in FIG. 4). To minimize the overall weight and maintain sufficient durability of the bat structure, however, it is generally preferred that substantially each of the dampeners 30 is discrete and strategically positioned at or near a single vibration anti-node. As described above, multiple dampeners may be located in parallel, i.e., at different radial locations, at or near a given anti-node.

The ball bat 10 may be constructed in any suitable manner. In one embodiment, the ball bat 10 is constructed by rolling the various layers of the bat 10 onto a mandrel or similar structure having the desired bat shape. The one or more dampeners 30, as well as any ISCZs, if used, are preferably strategically placed, located, and/or oriented, as shown and described above. The one or more dampeners 30 are preferably located at or near vibration anti-nodes in the tapered section 16, the handle 12, and/or the barrel 14 of the ball bat 10 to provide attenuation of vibrational energy in the ball bat 10.

The ends of the material layers are preferably “clocked,” or offset, from one another so that they do not all terminate at the same location before curing. Additionally, if varying layer orientations and/or wall thicknesses are used, the layers may be staggered, feathered, or otherwise angled or manipulated to form the desired bat shape. Accordingly, when heat and pressure are applied to cure the bat 10, the various layers blend together into a distinctive “one-piece,” or integral, construction. Furthermore, during heating and curing of the composite layers, the dampeners 30 preferably fuse with the surrounding composite material and become an integral part of the overall bat structure.

Put another way, all of the layers of the bat are “co-cured” in a single step, and blend or terminate together at at least one end, resulting in a single-piece structure with no gaps (at the at least one end), such that the barrel 14 is not made up of a series of tubes each with a separate wall thickness that terminates at the ends of the tubes. As a result, all of the layers act in unison under loading conditions, such as during striking of a ball. One or both ends of the barrel 14 may terminate together in this manner to form a one-piece barrel 14, including one or more barrel walls (depending on whether any ISCZs are used). In an alternative design, neither end of the barrel is blended together, such that a multi-piece construction is formed.

The described bat construction, incorporating one or more dampeners at or near vibration anti-node locations of the ball bat, significantly decreases the vibrational energy transmitted to the bat handle and the batter's hands. Accordingly, sting felt by the batter is significantly reduced or eliminated, and the “sweet spot” of the ball bat may be effectively increased. Dampeners may additionally be located in specific regions of the ball bat to provide increased flexure in those regions.

Thus, while several embodiments have been shown and described, various changes and substitutions may of course be made, without departing from the spirit and scope of the invention. The invention, therefore, should not be limited, except by the following claims and their equivalents. 

1. A composite ball bat, including a barrel, a handle, and a transition section joining the barrel to the handle, comprising: at least one dampener in at least one of the barrel, the handle, and the transition section, with substantially each of the at least one dampeners located substantially at an anti-node of a vibration mode of the ball bat.
 2. The ball bat of claim 1 wherein the at least one dampener is bonded to surrounding composite material in the ball bat.
 3. The ball bat of claim 1 wherein the at least one dampener is 0.008 to 0.020 inches thick.
 4. The ball bat of claim 1 wherein the at least one dampener comprises at least one of a viscoelastic and an elastomeric material.
 5. The ball bat of claim 1 wherein the at least one dampener comprises a plurality of discrete dampeners, with substantially each of the discrete dampeners located substantially at a single anti-node of a vibration mode of the ball bat.
 6. The ball bat of claim 1 wherein the at least one dampener comprises a plurality of dampeners arranged in parallel at a plurality of radial locations substantially at an anti-node of a vibration mode of the ball bat.
 7. The ball bat of claim 1 wherein the at least one dampener comprises a plurality of dampeners arranged longitudinally in series at approximately the same radial location in the ball bat.
 8. The ball bat of claim 1 wherein the at least one dampener comprises a plurality of dampeners located substantially at a plurality of anti-nodes of at least one vibration mode of the ball bat.
 9. The ball bat of claim 1 wherein at least one dampener is located substantially at the anti-node of the first bending mode of the ball bat.
 10. The ball bat of claim 1 wherein at least one dampener is located substantially at the anti-node of the first hoop mode of the ball bat.
 11. The ball bat of claim 1 wherein the barrel comprises at least two walls, and wherein at least one dampener is located in each of the barrel walls.
 12. The ball bat of claim 11 wherein the at least two walls of the barrel are separated by at least one ISCZ, and wherein at least one dampener is positioned against the at least one ISCZ.
 13. The ball bat of claim 1 wherein composite material in the ball bat is fused at at least one end to form a continuous load path between the at least one dampener and the composite material.
 14. The ball bat of claim 1 wherein the at least one dampener comprises a material having an axial elastic modulus that is 0.01 to 50% of an axial elastic modulus of neighboring composite material in the ball bat.
 15. The ball bat of claim 1 wherein the at least one dampener comprises a material having an axial elastic modulus that is 0.05 to 10% of an axial elastic modulus of neighboring composite material in the ball bat.
 16. The ball bat of claim 1 wherein the at least one dampener comprises a material having an axial elastic modulus that is 0.10 to 5.0% of an axial elastic modulus of neighboring composite material in the ball bat.
 17. A composite ball bat, comprising: a discrete first vibration attenuation element located substantially at the anti-node of the first bending mode of the ball bat; and a discrete second vibration attenuation element located substantially at the anti-node of the first hoop mode of the ball bat.
 18. The ball bat of claim 17 further comprising at least one discrete additional vibration attenuation element, with each of the at least one discrete additional vibration attenuation elements located substantially at one of the anti-nodes of the second bending mode of the ball bat.
 19. The ball bat of claim 17 wherein at least one of the first and second vibration attenuation elements is bonded to surrounding composite material in the ball bat.
 20. The ball bat of claim 17 wherein at least one of the first and second vibration attenuation elements comprises at least one of a viscoelastic and an elastomeric material.
 21. The ball bat of claim 17 wherein the first and second vibration attenuation elements each comprise at least one material having a lower axial elastic modulus than an axial elastic modulus of neighboring composite material in the ball bat.
 22. A composite ball bat, comprising: at least one discrete primary dampening element located substantially at the anti-node of the first bending mode of the ball bat; and at least one discrete secondary dampening element located substantially at one of the anti-nodes of the second bending mode of the ball bat.
 23. The ball bat of claim 22 wherein the at least one discrete secondary dampening element comprises at least a first dampener positioned primarily at the anti-node of the second bending mode located in a barrel of the ball bat, and a second dampener positioned primarily at the anti-node of the second bending mode located in a handle of the ball bat.
 24. A composite ball bat, comprising: a plurality of discrete means for dampening vibration, with substantially each of the discrete dampening means located substantially at a vibration anti-node in the ball bat and having a lower axial elastic modulus than that of neighboring material in the ball bat. 